a. Field of the Invention
The invention relates to a method for vacuum monitoring in vacuum switching tubes in which high voltage is applied between the contacts having a preselected contact spacing. In addition, the invention relates to the associated equipment for the implementation of the method, with a high voltage unit to generate a test voltage for the vacuum switching tube switching contacts opened at a defined contact stroke.
b. Description of the Prior Art
Vacuum switching tubes are used in insulated switching facilities, and other similar installations. Vacuum switching tubes are usually tested before delivery, using a setup based on the magnetron test principle. Due to modern production technology, a vacuum loss in the switching tube cannot occur in the normal case even after a long time period. It is required, nevertheless, to be able to check the internal pressure of a vacuum switch installed in the switching facility without having to disassemble the switching tube from its container.
For switching tubes without SF.sub.6 insulation, the user can check the internal pressure reliably by using mobile measuring instruments, e.g., measuring methods using the high-voltage testing modified magnetron apparatus with permanent magnets. Such known methods and measuring instruments cannot be applied to vacuum switching tubes installed in SF.sub.6 insulated switching facilities. In the hitherto commonly used high-voltage test in particular, the good insulation of SF.sub.6 would maintain the test voltage, and thus simulate a good vacuum, despite a possible leak in the switching tube during a test pulse. Therefore, this method is unable to distinguish reliably between vacuum and SF.sub.6, i.e., a leak in the switching tube.